Braze Pressure Welding (BPW) - A New Method for Joining Steel Pipes -

Braze Pressure Welding (BPW) with high frequency induction heating is a newly developed pressure welding technique using interlayer metals for welding the general steel pipes for pipe arrangement in buildings. BPW enables to make joints by solid-state welding in air using a flux sheet which is also developed for this technique. In this method, the interlayer metal is expected to play the primary role in making high performance joints. At a joining temperature, the melted interlayer removes contaminations from the joining surfaces of the base metals. Then the liquid filler is discharged from the joining interface by the joining pressure, and forms fillets at the gaps around the joint. In this stage, the joining pressure is relatively small, so the welding deformation can be restrained to a minimum. The fillets have the effects both on relaxing the stress concentration at the joint and on increasing the joining area, which contribute to the strengthening of the joint. Thus, the high quality pipe joining without the dispersion in joint properties due to welder’s skill can be performed. In this report, the concept and merits of BPW are explained, and the results of the investigation on the cleaning effect of the interlayer metal and the effects of fillet formation on strengthening the joint are discussed. The practical application of BPW in Japan is also introduced.